# Talk:Global Positioning System/Archive 1

## Wikipedia and GPS

Wouldn't it be useful to have GPS coordinates in all Wikipedia articles that are about locations? GPS links could be treated specially. For example, clicking on then could take the user to a map. --HelgeStenstrom 19:44, 9 Feb 2005 (UTC)

There's a project to do just that. Have you checked out any of the Rambot articles (say, Autaugaville, Alabama) lately? --Carnildo 20:05, 9 Feb 2005 (UTC)
The project is located at Wikipedia:WikiProject Geographical coordinates. Shawnc 02:19, 19 November 2005 (UTC)

## GPS Jamming

This might be a nice addition "In fact, we destroyed a GPS jammer with a GPS weapon," US Major General Victor Renuart told reporters at a briefing in Qatar Commking 21 October 2005

Which means the use of a GPS jammer is a superb idea! Electronics are very cheap to manufacture nowadays. GPS jammer plus ancient russian truck to run it around costs 1000x less then the command shelter or nuclear reactor or Ministry of Propaganda palace it is used to protect. It costs 50x less then the fighter-bomber and GPS-guided bomb America drops to destroy the jammer. So you can and you must deploy dozens of GPS-jammers and as long as one remains running the true asset is protected. Meanwhile USA will run out of budget dropping thousands of smart bombs on every jammer in sight. Also, one country could launch big GPS-jammer satellites in geostationary to black out its own territory and that would be difficult to destroy. —The preceding unsigned comment was added by 195.70.32.136 (talkcontribs) .

## What do GPS Coordinates look like?!

Can somebody post, as examples, GPS coordinates for some popular landmarks?

Cklester 16:47, 14 November 2005 (UTC)

Well, that depends on what format you want them in. Here are some samples:
N12.3456° W78.9012° — Degrees only (D)
N12° 34.567' W78° 12.345' — Degrees and minutes (DM)
N12° 34' 56.789" W78° 12' 34.567"; Degress, minutes and seconds (DMS)
12T E 408858 N 4569945 — Universal trans mercator (UTM)
These do not represent the same locations, but these do show some of the coordinate formats that you could have from a GPS unit. Some GPS units will let you switch between these different formats. Geocaching.com uses DM, or UTM. Google Earth uses DMS. Other places use degrees only.
If you wanted actual coordinates for popular landmarks, you'd also have to specify what Earth model (datum) you want to use for the coordinates. WGS-84 is the most up-to-date, so it is the one used, but my Garmin can be set to use any of over a dozen others. Val42 06:05, 15 November 2005 (UTC)

## GPS Accuracy

According to the 2001 Federal Radionavigation Systems report published by the United States Department of Transportation (DOT) and the United States Department of Defense (DOD) the Standard Positioning Service (SPS) is stated to have a global average predictable accuracy, 95% of the time, of 13 m horizontally and 22 m vertically. I'm curious as to where this article gets it's accuracy numbers from. I figure since DOT and DOD operate the system they would best know the accuracy of the system. I'd like to see some references cited for the accuracy numbers used in this article. Sure the SPS might be accurate to 5 meters, but how often, 1%, 10%, 50% of the time? Is this an average number or a best case number. See also 2001 SPS Performance standard (PDF) (2,101KB) --Dual Freq 00:47, 16 December 2005 (UTC)

In personal experience, with GPS receivers employing the current SirfStarIII chipset, an accuracy of better than 5 meters/15ft is the norm. Don't mind my thumb :) Kar98 00:30, 17 December 2005 (UTC)
I'd be very careful in believing what a GPS unit outputs for it's estimated position error (EPE). This is explained in a fairly decent manner here (disclaimer:I have no affiliation with this site). I can summarize by saying the EPE displayed by a GPS is pretty much just a guess based upon the dilution of precision of the satellites. Even the wikipedia article talks about error sources that are larger than 5 m. For example, this article states that ionospheric delay can account for errors greater than 10 m by itself, that's not counting the rest of the errors that an SPS single frequency user will have. How can the same article say GPS has an accuracy of 5 m in the introduction? This site (same disclaimer as above) goes into exhaustive detail on the issue of error. I guess the bottom line is, I think this article should provide accuracy numbers that have some sort of reference, not just what number a hand held GPS tells them most of the time. --Dual Freq 03:06, 17 December 2005 (UTC)
I quite agree, which is why I made sure to mention that I was talking from personal experience alone. Mark it down as Anecdotal_evidence :-) That's just me saying comparing the indicated position on the read-out with the actual position in the field, current consumer grade GPS receivers (tested a few, not just one) seem to have a consistent accuracy of better then 5 meters, without WAAS/EGNOS augmentation. Further anectodal evidence tells me that surveyor-grade units deliver accuracy of better than .3m, or 30 centimeters (after post-processing). Kar98 03:26, 17 December 2005 (UTC)
I agree it would be nice if the article gave a better reference for the accuracy claimed. I read parts of 2001 SPS Performance standard, and the question doesn't seem to have a simple answer that fits well in an introductory paragraph. I notice that the article is claiming accuracy as of 2005, and the SPS Performance Standard is from 2001. The performance standard also states that accuracy is improving as older satellites are replaced with newer ones, and even in 2001 the average SIS (signal in space) error was considerably less than 5 meters. The performance standard also specifically acknowledges that it does not include information about additional accuracy that can be attained through the use of dual-band (L1 and L2) receivers. And while the article does says that ionospheric delay is the largest source of pseudorange measurement errors, those errors can be corrected mathematically after the rough position of the receiver has been established. Also considering that many new GPS receivers include WAAS capabilities, I think the accuracy claimed in the introduction is probably a little optimistic, but plausable.
If you don't believe the 5 meter claim, I encourge you to change it to 13 or 22 or whatever you prefer, and site your source. If somebody else has a newer source that says it's gotten better since 2001, the accuracy of the article will just keep getting better, too. --Michaelfavor 17:33, 10 February 2006 (UTC)
I made a note of the question in the article by adding a {{Fact}} tag, and a mention of the 2001 performance standard. --Michaelfavor 18:23, 10 February 2006 (UTC)
FAA WAAS Fact sheet states "Using WAAS, GPS signal accuracy is improved from 20 meters to approximately 1.5 - 2 meters in both the horizontal and vertical dimensions." Interesting that this article says 5 m. Of course the FAA is worried about worse case and probably talking about 95% of the time. All I'm saying is the 5 m number should be qualified by whomever put it there. Is it a 50% time number? Is it anecdotal? Is it based on EPE numbers from a handheld GPS? --Dual Freq
I have made several change to the paragraph in question. How do you like it now? --Michaelfavor 15:18, 11 February 2006 (UTC)
Looks better, I might be nitpicking a bit here, but the DGPS article talks mainly about the USCG version and similar non-US systems which are listed as 1-3 m accuracy [1]. The centimeter systems are probably survey grade post processed or RTK and not USCG DGPS, right? --Dual Freq 15:43, 11 February 2006 (UTC)

Can Triangulation be implemented to improve the accuracy of GPS receivers, while also increasing the number of receivers.

## Correction for Military section

The article currently states the following:

Civilian GPS receivers are required to have limits on the velocities and altitudes at which they will report coordinates; this is to prevent them from being used to create improvised missiles

I believe this is an incorrect understanding, and offer the following instead:

Due to the potential for GPS receiver technology to be used in improvised weaponry, the US Government has classified civilian receivers for controlled export. This means that, in general, a US-based manufacturer can not export a receiver unless it has limits on the velocities and altitudes at which it will report position and speed information.

The same source can be cited; its just the arms control information. Davandron | Talk 19:19, 13 November 2006 (UTC)

## Locative games

There should be a link to locative games. The current version only includes Geocaching which is undoubtedly the most prominent example of a locative game, but there exist many others as well, especially in research. --Dendrolimus 19:57, 9 August 2006 (UTC)

## Misc

1. It is stated that NM takes 12.5 minutes to transmit. There needs to be an explanation of how a GPS receiver can determine a satellite's position in only a few seconds after being turned on.

2. Please describe what good the P-code could be if that transmission repeats only once a week. -- JM 7 September 2006

I do not agree that the Wiki article explains how the positions are calculated, except by using the NM signals. It states: "It then looks up the ephemeris data for each satellite, which was captured from the NM and stored in memory." The colorado.edu page you mentioned above is also vague on this point and, anyway, I believe the Wiki article should clarify this since it dances around the point. That is, how can a data message with a 12-minute period be useful to provide a quick position fix? And what possible use is the P-code with a weekly period? Those questions leapt off the page at me. I believe your Wiki article is deficient in these matters. JM 216.165.144.128 20:49, 9 September 2006 (UTC)
Pseudorange lines. There is only one spot in the world located at the 3 calculated distances from satellite 1, 2 and 3
("The entire nav message is 12.5 seconds [sic] long" -- I assume that's a typo.) You know too much and I know too little, so you're probably reading more into my original comment than I intended. If I knew the correct information to add, I'd do so. But I'm no expert, just an electrical engineer who recognized an inconstancy in the technical information section.
Above, you offered new and useful information: that the time is transmitted repeatedly and often enough in the 12.5-minute message that the time will be known within a few seconds. And I understand that from that you can determine distance to the satellites. But, as the article itself states ("By comparing the two, position and range, the receiver can discover its own location."), we need to know time (or distance) AND satellites positions. Are you saying you don't need to know the positions of the satellites -- that by visualizing the spheres alone there's only one place the intersection can be? Surely this is not the case; or if it is, then the Wiki quote is incorrect.
With just the time/distance, all you can determine is your position relative to the satellites, not your position relative to the Earth. If I'm wrong, then the Wiki statements (that we need to know where the satellites are) is incorrect.
The Wiki article states that the NM is 12.5-minutes long. In my view, that level of detail calls out for a further explanation of how such a slow-moving message could be useful. It is, after all, a "Technical description" section. If you believe that the details I'm requesting are inappropriate for Wiki, then I assert that you shouldn't be be priming the pumps with such minutia as bit rates and the like. You can't have it both ways.
• "In order to facilitate quick acquisition, the time is repeated every six seconds and the position is repeated every 30 seconds [or whatever] during the entire 12.5-minute navigation message."
• "In order to facilitate quick acquisition, the time and position information are repeated numerous times throughout the entire 12.5-minute navigation message."
If that's true, then I propose one of those be added to the article and I'd be satisfied. JM 216.165.144.128 02:44, 11 September 2006 (UTC)

The www.gpsnews.org link is questionable. The change at 11:39 on Mar 24, 2006 from 151.37.154.185 did nothing useful - just added this link at the top of "Other Information". Is this the kind of thing that should be removed? It doesn't seem to me to add anything useful, and in any case is only "news" related to GPS receivers, not the GPS itself... -- JohnRobert 12:53, 18 April 2006 (UTC)

Anyone have a Code vs. Carrier Phase description?

There is a good explanation of this at Code-Phase GPS vs. Carrier-Phase GPS -- Michaelfavor 16:45, 23 February 2006 (UTC)

Should the Geocaching section say that the pasttime is popular with "both children and adults"? Surely that makes it popular with everyone, and that phrase is therefore redundant?

Check my change. Is that good? If not, you can fix it- be bold. Happy editing.--Adam (talk) 16:38, 14 February 2006 (UTC)

Is it really necessary that the receivers have a clock with good short term accuracy? I thought that the signals from the satellites are such that by simply comparing them, the receiver can tell the time difference, without much of a clock. For instance, if all satellites send the sequence 12345678901234567890... synchronously, with one digit coming every millisecond, and the receiver sees two sequences which have an offset of 3, then he knows that the signal from the one satellite travelled 3 (or 13, or 23...) milliseconds longer than from the other, without any need for a clock.

But I don't know the implementation details. Do we have any experts here? AxelBoldt

Messages are typcally referenced against an on-board quartz crystal oscillator/clock, which provides a timebase that all the others are compared to. The signals are individually weak, fading, full of interference -- comparing them directly with one another is harder than receiving them all independently, and comparing. Single channel receivers (now mostly obsolete) also had no other way of doing it. The Anome

I see, thanks. AxelBoldt

But, to be sure, the "short term accuracy" needed is not like a cesium clock. The internal crystal clock that The Anome is talking about needs to keep from drifting more than, say, a few nanoseconds (or tens of nanoseconds) during the time needed to "take a fix". Each nanosecond of drift corresponds to a light-nanosecond (about 30 cm, or one foot) of position inaccuracy, so 100 ns of drift means 30 meters of error - more than most modern units allow, typically. (Somebody check my math; I may have dropped a decimal point somewhere.) Also, since crystal frequencies vary with temperature change, all modern receivers (so far as I know, but I don't claim to be an expert) keep track of their crystal's behavior at various temperatures (with an internal thermometer), even when the GPSr is turned off, so that it will "wake up" with a fairly good resistance to drift. - Rootbeer 2002-04-07

Hence the importance of the Allan variance -- and Quartz crystals are really quite good clocks over suitably short periods (they're not bad over longer periods, either...) But that's a subject for another article. The Anome

Some officials believe that jammers could be use to attract the precision-
guided munitions towards noncombatant infrastructure, other officials believe
that the jammers are completely ineffective.


That sounds like a very interesting debate. Do we have sources? I'd be interested in knowing more.

Best, --257.47b.9½.-19 00:12, 4 Apr 2004 (UTC)

Question about relativistic corrections of satellite time (shouldn't they be rather opposite?).

"The clocks on the satellites are also affected by both special, and general relativity, which causes them to run at a slightly faster rate than do clocks on the Earth's surface. This amounts to a discrepancy of around 38 microseconds per day, which is corrected by electronics on each satellite."

Why is it slightly faster and not slower rate, and why 38 us/day while, according to my back-of-envelope math, the SR effect for the fastest possible satellite (at 8 km/s) is slowing of time by about 30 us/day and GR effect is rather negligible (and subtracting from those 30 s/day). Is it only my math? And if so could anyone provide the right one? Jim 18:05, 2004 Jul 8 (UTC)

SR slows the clock by about 7 us/day. GR speeds it up by about 45 us/day. The article is correct. See http://www-astronomy.mps.ohio-state.edu/~pogge/Ast162/Unit5/gps.html Amcfreely 14:23, 18 October 2005 (UTC)

" The receiver computes the distance to each of the four satellites by the difference between local time and the time the satellite signals were sent (this distance is called a pseudorange ). It then decodes the satellites' locations from their radio signals and an internal database. The receiver should now be located at the intersection of four spheres, one around each satellite, with a radius equal to the time delay between the satellite and the receiver multiplied by the speed of the radio signals. However, since the receiver does not have a ultra-precise reference clock, The intersection point gives the precise location of the receiver. If elevation information is not required, only signals from three satellites are needed. "

This does not make too much sense to me: without a highly precise local time (i.e. an atomic clock), one does not know the time delay with respect to a satellite, but only the time differences between the messages from the satellites. This yields 3 hyperboloids of revolution, not 4 spheres. I've checked on various sites and they also talk of hyperboloids. David.Monniaux 08:12, 18 Jul 2004 (UTC)

If the receiver had a highly precise local time it would ony have to use 3 satellites to calculate a position in space as a intersection of three spheres. Actually it get 2 point where the spheres intersect but one of them is far out in space (3-6 earth radius). Using four sattelites the receiver can also calulate the fourth dimension time and get an accurate time. I think the talk about hyperboloids is an other way to look at it as the interferens pattern of the phase of the radio signal as the DECCA or Loran system did. And with 2 diffrent frequencies the receiver is able to make corrections between them.

User Biker from Swedish Wikipedia [3]

Uh, just to clarify a little. If you have a pair of satellites with a difference in transmission time between them, you have two foci and the difference of your distance between them. The set of points where the difference to the distance between two fixed points is constant is a hyperboloid in 3D. If you had precise local time, then you'd have the intersection of two spheres - which is NOT two points (one far in space). The interesection of two spheres is a circle. --Rich0 19:12, 20 Nov 2004 (UTC)

The discussion of the L2 frequency needs to be cleaned up. At one point, the article mentions its use with high-end receivers, but in other locations it sounds like the signal is available for military applications only. The article fails to discuss the multiple segments of the GPS system: control, space, and user. I shall try to make some changes over the next few days once I have a chance to review my notes. Richss 05:28, Sep 6, 2004 (UTC)

Regarding trilateration vs. triangulation: By definition, trilateration seems correct. Doing a google search, it seems that many knowledgable sources also use this term. However, much of the literature that I have read regarding GPS and how it works previously, uses the term triangulation. I would suggest that perhaps we keep trilateration, but mention this discrepency to alleviate some confusion. Richss 14:18, Sep 6, 2004 (UTC)

There is a mistake in this article. ${\displaystyle n}$ reference points, whose distance differences to the unknown position are known, give ${\displaystyle {\frac {n*(n-1)}{2}}}$ (semi-)hyperboloids. 3 points are not enough in general, since all hyperboloids are mirror-symmetric to the plane in which the points lie and therefore the solution set is mirror-symmetric to this plane too.

## System reliability

The article that is the basis for this section, GPS users must plan for outages, is basically FUD in support of the competing Galileo system. There are currently at least 6 on-orbit spare SVs. As of late 2002, there were 14 IIR SVs ready for launch. Lockheed Martin is building another 7 IIR-Ms and the IIF block is under design. See http://www.agcc.gov.au/gnss/GNSS_Platforms.aspx, http://gps.faa.gov/FAQ/faq-gps.htm, http://www.navcen.uscg.gov/gps/modernization/default.htm, and http://tycho.usno.navy.mil/gpscurr.html. Amcfreely 02:20, 16 October 2005 (UTC)

In the light of the above, I would trim the existing contents of the System Reliability section which I added simply to state that the reliability has been questioned, then append the above figures in conjunction with information on the numbers of existing satellites and their ages. I'm not myself familiar enough with the program to make the change myself (it's reasonable to question reliability without deep knowledge, but unreasonable to defend it). With such a critically important system reliability does need very careful scrutiny and attention. In the case of the space shuttle program, reliability was undermined by assumptions and complacency, but the GPS figures above do seem reassuring.

I do think that a System Reliability section is needed for such a critical system, hopefully only to reassure. Of course it will have to be revised often, but Wikipedia can cope. Pol098 00:35, 17 October 2005 (UTC)

## System reliability, continued

The GPS signal is more fragile than might be supposed. A network of at least 24 satellites is required for full coverage. Satellites cannot be repaired and have a limited life. As of 2005:

• there are 28 satellites in orbit, of which 16 are already beyond their design life—the oldest have nearly reached twice their design life.
• The failure rate is about two satellites per year.
• The launch rate of new satellites is about two per year.

If the older satellites start to fail faster—which may well happen— and if the launch rate cannot be increased proportionately, full coverage could be lost. The article GPS users must plan for outages discusses this possibility from the perspective of a backer of the competing Galileo system. Fortunately, this is not a concern in practice for at least two reasons. First, the Air Force monitors the health of SVs closely and maintains at least one on-orbit spare in each orbital plane. Second, the Air Force could easily increase the launch rate with SVs and ELVs already on hand.

i cut and pasted this section from the main article to this talk page, in case anybody thinks the discussion is worthwhile, or wants to add references. as it is, the whole section is a little too speculative for my taste, and i dont think it belongs in the article. --Michaelfavor 20:15, 21 January 2006 (UTC)
My reply to the "reliability concern" is not speculative at all. It is documented that there are on-orbit spares, a number of spares on the ground, and easily the launch capacity to get them into orbit. For references, see the System reliability discussion up-page.Amcfreely 15:46, 23 January 2006 (UTC)
No offense was intended. My comment was about the section as a whole. I actually think your sentences add balance to the section, and improve it quite a bit. Here is my question: Is it worth-while to add references to support the sensible parts of this section, or is the whole section so "non-notable" that I could be completely eliminated from the article without objection?
In the up-page discussion, you seemed to be of the opinion that the article supporting the original assertions was "FUD". Another user says up-page it's an important question to consider in a system this critical, and maybe he is right. I could go either way, remove the whole section or add references as needed. The launch rate from 1990 through 1995 was about four satellites per year, and I suspect the only reason the rate is currently two per year is because the pattern is full, and the launch rate is limited to match the failure rate. The main article is not suffering from being too short. If we agree that this question is sufficiently non-notable, we can remove it and increase the signal to noise ratio. -- Michaelfavor 23:39, 23 January 2006 (UTC)
The particular article is FUD, though I do agree that reliability is an important concern in a system so widely used and relied on. Amcfreely 00:46, 25 January 2006 (UTC)
You should consider that rockets sometime fail or explode on launch, so having spare satellites on the ground does not mean they will arrive in orbit. A big nasty solar storm or a new supernova anywhere in our trusty old Milky Way could kill multiple GPS satellites in orbit. Also, GPS satellites are a valid military target, because they have secondary, but direct military functionality (watch strategic missile launches) so an advanced adversary could decide to shoot down one or more of them (say Red China in a few years' time in a Taiwan war). Or a console knight (privateer or north korean) could hack the system and bring the GPS down. You definitely need to consider what you would do in a GPS-less world.—The preceding unsigned comment was added by 195.70.32.136 (talkcontribs) .
Like any other modern military system, GPS satellites are hardened against radiation (natural and man-made). A solar storm will not kill them. A supernova close enough to destroy them would present much more serious problems for earth. GPS satellites orbit over 12,000 miles high, which is 80 times higher than the space shuttle flies. To my knowledge no nation (including the U.S.) has ever had an anti-satellite capability for that altitude. The GPS satellite constellation is highly redundant, not even including orbital spares. Just destroying a few doesn't greatly degrade the system. Therefore multiple repetitive intercepts would be needed, which would take considerable time. That would of course be an act of war inviting major retaliation, so (even if possible) it wouldn't be done lightly or because of a regional conflict. There is no rational basis for "hacking" the GPS system. If so an adversary could hack spy satellites and use them, or any other military system using encryption. Most current military and certified civilian GPS-aided navigation systems are designed to work without GPS. E.g, GPS-guided munitions generally have a strap-down inertial navigation system for fallback use if the GPS signal is lost. Aircraft using GPS don't rely on that as a sole method. None of this is new -- any navigation system can be lost at any time for many reasons. Although highly redundant, hardened and secure, this includes GPS. Therefore all mission-critical navigation systems and techniques (whether GPS or other) are already designed to sustain the loss. Joema 20:41, 25 May 2006 (UTC)

## GPS / WAAS relocation

According to this Public domain press release a WAAS satellite is relocating and might affect GPS/WAAS usage on the east coast of the US.

The move of the AOR-W satellite to the west may have a significant impact on non-aviation users on the East Coast. In its new position, the AOR-W satellite will appear lower on the horizon to users situated at ground level. As a result, the satellite may be obstructed by mountains, buildings, trees, or other types of obstructions that sit to the west of the user.

Sounds like a temporary problem and they say it will be resolved by Fall of 2006. Is this something that merits mentioning in the WAAS or GPS articles? Even though it's temporary doesn't it say something about reliability? --Dual Freq 16:26, 28 January 2006 (UTC)

## Talk page archive

Isn't it customary to archive talk pages rather than delete things from them? See also: Wikipedia:How to archive a talk page. --Dual Freq 03:14, 10 February 2006 (UTC)

I've been trying to follow the suggestions in Wikipedia:Refactoring talk pages, about editing talk pages in the context of signal-to-noise ratio. It says: "Think what the talk page is about and remove anything superfluous that would not help future editors". A couple of the talk-page sections I erased were unsigned comments, fairly non-sensical questions, almost gibberish. I also erased a couple of sections that were basically to-do list items that were already completed without any controversy. I didn't see how keeping them would be helpful to future editors. My intent was not to delete anything controversial. Please feel free to restore any parts you feel are relevant.
One of the wonders of Wikipedia is that the old content is never really deleted, because it is always available in the page history. This gives us the freedom to limit the noise. I believe one of Wikipedia's greatest strengths is the high signal-to-noise ratio, and erasing useless and outdated content is vital to maintaining that quality. --Michaelfavor 12:03, 10 February 2006 (UTC)
You may as well remove the comments I made above about WAAS and GPS Accuracy, neither seem to be useful and pretty much were ignored. I still think GPS accuracy is a bit overstated on the main page, but why should wikipedia use DOD/DOT published accuracy information when it can use more reliable anecdotal accuracy numbers. --Dual Freq 12:24, 10 February 2006 (UTC)
I think the your comment above about GPS accuracy is useful and should not be removed. I see it as a "to-do" item that has not been completed yet. If you feel strongly about it, why not simply edit the article yourself? --Michaelfavor 17:08, 10 February 2006 (UTC)

## Bug in article history

The history page for this article shows the oldest revision as being on 2001-02-19 [4], yet that revision does not identify the article as a new article as some other contributions by the same user to, but is marked by the user as a minor revision, without even an edit summary, and the article seems to be fairly well developed. It seems unlikely to me that was actually the first edit of the article.

The "older version" link within that version of the article links to the 2002-08-02 [5] version of the article. Presumable, continued clicking on the "older version" link would eventually lead back to the 2001-02-19 version, and continue in an infinite loop. -- Michaelfavor 17:09, 13 February 2006 (UTC)

See [6]. The policy of keeping the page history did not exist in the beginning of Wikipedia's existence, so the page history of that time is lost. Pfalstad 17:54, 13 February 2006 (UTC)

## GPS tracking

Discussion of GPS tracking has been moved to Talk:GPS tracking.

## New L1, L2, and L5 signals/Galileo interoperability/E5ab

The information in, e.g., http://www.navcen.uscg.gov/cgsic/meetings/summaryrpts/45thMeeting/13%20CGSICAJVD2.ppt, http://gps.faa.gov/gpsbasics/GPSmodernization.htm, http://www.navcen.uscg.gov/gps/modernization/default.htm, http://www.gpsworld.com/gpsworld/article/articleDetail.jsp?id=12195&pageID=1&sk=&date=, http://www.cast.uark.edu/local/GEOG4593/readings/EngeAIAC03.pdf would make useful additions to the article. It's difficult to tell what the most recent status of the GPS signal modernization effort is. Is anyone more familiar with the details? Does the information belong on a separate page? Amcfreely 06:32, 26 April 2006 (UTC)

Sorry about deleting this note, I'm not sure what happened, but I'll try not to do it again. --Dual Freq 02:48, 27 April 2006 (UTC)
Found a good article; lots of details. Seems like civilan L2 and L5 should have their own sections, or even pages (gps modernization).